How to add column value plus users input in PHP update query - php

Question

Not sure if this is even possible, I am trying to get it to where "ItemA" has a value of 100 in the database. Which I have assigned a value to problem, what I really want is if a user inputs 50 into an input field, that "ItemA" value will now show 150 when it is called back in a select query. I am unsure of how to add the value in a column and a users input together.
I am new to PHP and SQL, so please forgive me. Any help is greatly appreciated and I thank you for your time!
The PHP that I have:
<?
$payout = $_POST["payout"];
$payouts = $_GET["payout"];
$withdraw = $_POST["bank_withdraw"];
$cashspent = $_POST["cash_spent"];
$servername = "localhost";
$username = "*****";
$password = "*****";
$db = "*****";
$conn = new mysqli($servername, $username, $password, $db);
if ($conn->connect_error){
die("Connection failed: ". $conn->connect_error);
}
$sql = "UPDATE finances SET payout = '$payouts' + ? WHERE finance_id = 1";
$stmt = mysqli_stmt_init($conn);
if ( ! mysqli_stmt_prepare($stmt, $sql)){
die(mysqli_error($conn));
}
mysqli_stmt_bind_param($stmt, "ii",
$payout,
$payouts
);
mysqli_stmt_execute($stmt);
In this example, I am trying to have it where a user is able to add the two values from what is already in the database.
Item in database (payout) = 100
Input from user = 50
Item from database + input from user = 150, showing in database

Answer 1

if I understand your question correctly there are 2 parts:
Select payout from database and add it to the user input.
update the value in the database
For 1) select the payout from the database $select_sql = "SELECT payout FROM finances WHERE finance_id = 1"; and you could use a variable such as $increasedPayout and assign this new variable $increasedPayout = $payouts + $select_sql;
and then for 2) use the $increasedValue variable in your SQL UPDATE statement.
$sql = "UPDATE finances SET payout = '$increasedPayout' WHERE finance_id = 1";